(1) Field of the Invention
The invention relates to a deodorant or antiperspirant stick based on an oil-in-water dispersion/emulsion for the application of water-soluble active ingredients to the skin.
(2) Description of Related Art, Including Information Disclosed Under 37 C.F.R. §§1.97 and 1.98
Standard commercial deodorants and antiperspirants are mostly formulated as sprays or as sticks; there are also roll-on preparations and creams in the market. Many stick antiperspirant preparations are formulated as anhydrous suspension sticks. Preparations of this type leave behind a pleasant dry feel on the skin for the user following application. However, effective release of the water-soluble antiperspirant active ingredients from such preparations is limited (cf.: Chemistry and Technology of the Cosmetics and Toiletries Industry, edition D. F. Williams and W. H. Schmitt, London: Blackie, 1996, 2nd edition, p. 326), and in most cases the feeling of freshness valued by many consumers is not achieved. The anhydrous preparations, in particular those based on volatile silicone oils, have the disadvantage that the dispersed active ingredients readily lead to visible product residues on skin and clothing. Furthermore, such preparations are relatively expensive since the oil components are more expensive as active ingredient carriers than water. Compression during application often results in the loss of oil, which reduces the cosmetic acceptance of these preparations for the user.
Compared with anhydrous sticks, as are known, for example, from WO 94/24997 A1 and WO 00/67713 A1, emulsion sticks, as are disclosed, for example, in WO 98/17238 A1, EP 281 288 A2, DE 2 335 549, U.S. Pat. No. 4,725,431, EP 617 952 A1 and EP 291 334, have a number of advantages. Replacing the wax and oil additives with water makes the emulsion sticks more cost-effective to manufacture. The emulsified waxes convey a soft, gentle feel on the skin, and, finally, water-soluble cosmetic active ingredients (i.e., in particular, antiperspirant active ingredients) can more readily be released onto the skin since they are already present in dissolved form in the aqueous phase of the emulsion.
WO 02/017870 A2 discloses antiperspirant sticks without a W/O emulsifier or high melting wax which contain a siliconized polyamide as a consistency regulator or structurant. According to patent claim 1 of WO 02/017870 A2, the hydrous phase forms the internal phase, i.e., the dispersed phase, and the gels disclosed are water-in-oil emulsions.
WO 02/032914 A1 discloses, with reference to several exemplifying embodiments, hydrous antiperspirant sticks based on a water-in-oil emulsion which contain acylated cellobiose as the consistency regulator or structurant and contain a high fraction of the silicone and hydrocarbon oils which are unfavorable according to the invention, and furthermore do not contain oil-in-water emulsifiers or a high melt wax.
Since the emulsion sticks of the cited prior art are formulated on the basis of a water-in-oil dispersion/emulsion, the water-soluble active ingredients are present in the inner, dispersed phase and, following application, must first migrate through the outer, lipophilic layer in order to reach their site of action on the skin. The known water-in-oil emulsion sticks thus have disadvantages which are similar to those of anhydrous suspension sticks with regard to the availability of active ingredient.
DE 19749819 A1 discloses water-containing and oil-containing, wax-free antiperspirant sticks based on an oil-in-water emulsion. Sticks of this type have inadequate cosmetic properties, leave behind unpleasant sticky and visible residues and exhibit a stability which is insufficient for prolonged use. One example with glycerol monostearate as W/O emulsifier and octyldodecanol as oil component has a medium-firm consistency and a greasy feel on the skin and begins to soften at just 50° C.
WO 99/59537 A1 discloses hydrous cosmetic sticks which comprise wax components with a melting point of >50° C., nonionic water-in-oil emulsifiers, a nonionic oil-in-water emulsifier with an HLB value of more than 7 and a polyol. Some of the sticks contain oils which are liquid at 25° C. but which, instead of being incorporated at the beginning of the emulsion process as in the sticks of the present application, are stirred in as a pre-emulsified concentrate, for instance a micro-emulsion or PIT emulsion, during the cooling phase of the stick mass at a temperature of 55° C. This type of production method is needed in order not to endanger or even destroy the stability of the system for a dispersion of lipid and wax crystals. Sticks of this type likewise have inadequate cosmetic properties, can leave behind unpleasant sticky and visible residues, and exhibit a stability which is inadequate for prolonged use.
WO 02/083091 A1 discloses structured antiperspirant compositions in the form of a microemulsion which represents an oil-in-water microemulsion or a water-in-oil microemulsion or a bicontinuous phase, depending on the kind and quantity of surfactants, but in which the bicontinuous phase predominates overall. The (transparent) microemulsions are condensed by an oil-soluble or oil-dispersible “structurant.” The oil-soluble or oil-dispersible “structurant” is chosen from among esters and amides of 12-hydroxystearic acid, esters and amides of di- and tricarboxylic acids, sterols, sterol esters such as oryzanol, cellobiose fatty acid esters, sugar esters such as acylated maltose, and non-crosslinked oil-soluble or oil-dispersible polymer oil phase condensing agents such as the commercial product Kraton G. Ionic emulsifiers with an HLB value from 2-15, preferably with an HLB value under 12, are also incorporated. Polyols are disclosed as optional only. This document does not disclose the possible significance of the solubility parameters of W/O emulsifiers and oil components being matched with one another. The structural difference between these compositions and the oil-in-water dispersion/emulsion sticks of the present invention, which are not microemulsions, becomes particularly clear because of the high fraction, namely 19-66% by weight relative to the overall composition, of silicone and (paraffinic) hydrocarbon oils which all exemplifying embodiments disclose but which are unfavorable according to the invention.
Published Application Nos. DE 199 62 878 A1 and DE 199 62 881 A1 disclose deodorant or antiperspirant creams based on an oil-in-water emulsion which have, at 21° C., a viscosity of at least 50,000 mPas, preferably in the range from 200,000-1,500,000 mPas, i.e., they are in viscous to highly viscous paste form. These creams comprise wax components with a melting point of >50° C., nonionic water-in-oil emulsifiers, but not an ethylene glycol ester or a pentaerythryl ester, nonionic oil-in-water emulsifiers with an HLB value of more than 7, and a polyol. Being soft creams, they can be applied either by using only the fingers, which is rejected by many consumers as being impractical, or by pouring the creams into special applicators, which are significantly more expensive than the stick sheaths for the deodorant or antiperspirant sticks according to the invention. If, after being heated and mixed, the compositions disclosed in DE 199 62 878 A1 and DE 199 62 881 A1 were cooled statically, i.e., without stirring, then stick-like compositions would be obtained which have overall unfavorable application properties, such as poor haptics and/or inadequate stability, for example, as a result of phase separation or the formation of water condensation, since the emulsifiers and the oils are not matched to one another as in the present invention.
DE 10 2004 036 689.6 was not published before the filing date of DE 10 2005 002523.3, from which this application claims priority. DE 10 2004 036 689.6 discloses deodorant or antiperspirant sticks in the form of an oil-in-water dispersion containing at least one lipid or wax component with a melting point of >50° C., at least one nonionic oil-in-water emulsifier with an HLB value above 7 within a nonionic oil-in-water emulsifier system with an average HLB value between 10 and 19; as a consistency regulator and/or water binder, at least one nonionic water-in-oil emulsifier with an HLB value of greater then 1.0 and less than/equal to 7.0, which can form liquid crystalline structures with water alone or with water in the presence of a hydrophilic emulsifier, and at least one oil which is in a liquid state at 20° C. and is not a fragrance component or essential oil--the maximum deviation between the (average) solubility parameter of all the constituent oils and the (average) solubility of the water-in-oil emulsifier or emulsifiers being −0.7 (cal/cm3)0.5or +0.7 (cal/cm3)0.5 in the presence of linear saturated fatty alcohol as the water-in-oil emulsifier or part of a water-in-oil emulsifier, respectively, and −0.4(cal/ cm3)0.5or +0.7 (cal/ cm3)0.5in the presence of water-in-oil emulsifiers other than linear saturated fatty alcohols in the absence of linear saturated fatty alcohols as a water-in-oil emulsifier, respectively; at least one water-soluble polyhydric C2-C8 alkanol with 2-6 hydroxyl groups and/or at least one water-soluble polyethylene glycol with 3-20 ethylene oxide units; 5% to less than 50% by weight of water relative to the whole composition; and at least one deodorant or antiperspirant agent; where the stick exhibits a penetration force value in the range of 200-600 gram-force (g-force) at a depth of 5.000 mm (five millimeters) and a maximum electrical resistance of 300 kΩ(Kiloohm). It has been discovered, however, that glycerol monostearate and glycerol distearate, the preferred W/O emulsifiers in DE 10 2004 036 689.6, can present difficulties with respect to large-scale production, particularly as concerns product consistency.